diff --git a/library/asn1write.c b/library/asn1write.c
index 053dbb669..6c2a71f00 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -78,9 +78,11 @@ int mbedtls_asn1_write_len( unsigned char **p, const unsigned char *start, size_
         return( 4 );
     }
 
+    int len_valid = 1;
 #if SIZE_MAX > 0xFFFFFFFF
-    if( len <= 0xFFFFFFFF )
+    len_valid = ( len <= 0xFFFFFFFF );
 #endif
+    if( len_valid )
     {
         if( *p - start < 5 )
             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
@@ -92,10 +94,10 @@ int mbedtls_asn1_write_len( unsigned char **p, const unsigned char *start, size_
         *--(*p) = 0x84;
         return( 5 );
     }
-
-#if SIZE_MAX > 0xFFFFFFFF
-    return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
-#endif
+    else
+    {
+        return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+    }
 }
 
 int mbedtls_asn1_write_tag( unsigned char **p, const unsigned char *start, unsigned char tag )